1. Field of the Invention
This invention relates to a mobile machine, such as a fork lift truck, with at least two electrical drives, at least one electrical control system, and at least one electric power source.
2. Technical Considerations
During the deceleration of an electrical drive system of a mobile machine, such as a traction drive system of an industrial truck for example, the electrical drive system functions as a generator and converts kinetic energy into electrical energy. If a battery is used as the energy source, this electrical energy can be used to recharge the battery. Because the energy to operate the electrical drive was previously taken from the battery, the charging capacity of the battery is generally sufficient to absorb the energy released during deceleration. However, if a heat engine with a connected generator or a fuel cell system is used as the energy source, for example, the battery is unable to absorb all of the electrical energy generated during deceleration and the generated electrical energy must be discharged in some other way. In addition to the direct conversion of the electrical energy into heat, it is also possible to use the generated energy to charge a conventional electrical buffer storage mechanism, such as a high-capacity capacitor, for example. Although such conventional buffer storage mechanisms are typically large enough to absorb a sufficient amount of the generated energy even during a long downhill run of the mobile machine and, thus, to ensure the braking action, these conventional buffer storage mechanisms are still expensive and take up a lot of space in the mobile machine. If the capacity of the buffer storage mechanism is insufficient to absorb all of the energy generated under all expected operating conditions, an additional braking resistance must be provided, which also takes up space and requires a complex cooling system.
Therefore, it is an object of the invention to provide a mobile machine, such as an industrial truck, with at least two electrical drives and which safely diverts the electrical energy released during deceleration of one of the electrical drives easily and economically.